This section provides background information related to the present disclosure which is not necessarily prior art.
1. Technical Field
The present invention relates to a chemical liquid feeding device, and more particularly, to a chemical liquid feeding device capable of feeding uniformly chemical liquid required in a semiconductor fabrication process without pulsation.
2. Discussion
A semiconductor fabrication process consists of three steps: design of a wafer circuits, processing of the wafer and assembly/inspection. In an etch process and cleaning process of the wafer processing process, there are used chemical liquids for etching or cleaning the wafer (hereinafter, referred to as chemical liquids).
As is known in the art, the semiconductor fabrication process is a process of producing a product with high precision. Therefore, an exact mixing ratio of the chemical liquids used in this semiconductor fabrication process and uniform feeding of the chemical liquids are very important.
The uniform feeding of the mixing ratio is made by feeding device including a diaphragm or bellows pump. FIGS. 1 to 3 show this conventional feeding device: FIG. 1 is a plan view showing a main structure of a conventional chemical liquid feeding device; FIG. 2 is a front view showing an operation of the chemical liquid feeding device of FIG. 1; and FIG. 3 is a graph showing suction and discharge processes according to time of the chemical liquid feeding device of FIG. 1.
As shown in FIG. 1, the conventional feeding device 200 includes two bellows pumps 210, 212. The two bellows pumps 210, 212 are installed so that they face with each other with a body of the feeding device being placed therebetween and operate so that time points of suction stroke and discharge stroke of the pumps are not agree with each other (refer to FIG. 3). Accordingly, the conventional feeding device 200 has an advantage of capable of feeding a chemical liquid uniformly since the pump 212 discharges the chemical liquid when the pump 210 sucks in the chemical liquid.
However, this conventional chemical liquid feeding device has the following disadvantages due to the installation structure of the pumps 210, 212.
First, there is a limitation in increasing a flow rate.
The conventional chemical liquid feeding device 200 consists of two facing bellows or diaphragm pumps. Accordingly, it is required for the conventional chemical liquid feeding device 200 to enlarge a size of the bellows or diaphragm to increase the flow rate but it is difficult to enlarge the size of the bellows or diaphragm due to the structure or cost.
Second, it is difficult to clean the pump due to the chemical liquid and it is also difficult and dangerous to replace the pump.
In the conventional chemical liquid feeding device 200, since the bellows pumps 210, 212 are installed with being laid on their sides, a large amount of the chemical liquid is always remained in an inside of the pumps 210, 212 (particularly, in folding portions in the bellows pump which expands and contracts). However, most of the chemical liquids 300 are generally harmful to human body and there is high risk of damage to the human body due to leakage of the chemical liquid when a connection port is disconnected and reconnected for the replacement of the pump. Also, in a case that a fine abrasive for cleaning or washing a semiconductor wafer is contained, there is a high possibility that the abrasive is remained in the pumps 210, 212 to abrade the major parts (the folding portion of the bellows pump or diaphragm of the diaphragm pump) of the pumps 210, 212.
Therefore, in the conventional chemical liquid feeding device 200, there occur problems that the bellows pumps 210, 212 cannot be used until their predetermined life time and an efficiency of pumps is remarkably lowered according to a long time use.
Third, considerable pulsation is generated when feeding the chemical liquid.
The conventional chemical liquid feeding device 200 can generally feed the chemical liquid uniformly since the two bellows pumps 210, 212 operate so as to have opposite time points of suction and discharge as described above.
However, in the conventional chemical liquid feeding device 200, since a period of conversion from a time point of maximum discharge T1 by the pump 210 to a time point of maximum discharge T3 by the pump 212 is clearly distinguished and is long as shown in FIG. 3, pulsation according to repetition of the suction and discharge strokes is very remarkable and a pressure difference at a time point T2 of conversion from T1 to T3 is very large.
Accordingly, the conventional chemical liquid feeding device 200 has a disadvantage that large and small vibrations and noises are generated in the chemical liquid feeding process due to the pulsation and also has a disadvantage that final discharge pressure of the chemical liquid becomes irregular due to pressure reduction generated at every time point of conversion of the discharge stroke.